(1) Field of the Invention
This invention relates to a fluorine based aqueous dispersion, a process for preparing the same, and a fluorine based matte anionic electrodeposition coating composition containing the same.
(2) Description of the Prior Art
An aqueous coating composition has widely been used, because it uses water as a medium and is free of troubles about working atmosphere, danger of fire, and so forth. However, recent diversification in user's need shows a tendency to lose interest in feeling of metallic luster and highly demands matte coated film which provides grave feeling.
Japanese Patent Application Laid-Open No. 213058/83 discloses a resin composition for use in a matte anionic electrodeposition coating composition, which contains a product obtained by heating an aqueous emulsion containing .alpha.,.beta.-ethylenically unsaturated polycarboxylic acid resin and an epoxy compound as the film-forming components. The .alpha.,.beta.-ethylenically unsaturated polycarboxylic acid resin is a copolymer obtained by copolymerizing (a) .alpha.,.beta.-ethylenically unsaturated carboxylic acid, (b) a hydroxyalkyl-containing ester, amide or amide derivative of .alpha.,.beta.-ethylenically unsaturated carboxylic acid and (c) an alkyl ester of .alpha.,.beta.-ethylenically unsaturated carboxylic acid. The film finally formed from the above copolymer has such drawbacks as to show poor properties in weather resistance, chemical resistance, etc. On the other hand, the epoxy compound to be reacted with .alpha.,.beta.-ethylenically unsaturated polycarboxylic acid resin may includes epoxy compounds containing at least one epoxy group in one molecule. However, the use of a monoepoxy compound having one epoxy group in one molecule as the epoxy compound for forming a matte film has such drawbacks that the monoepoxy compound has no compatibility with the polycarboxylic acid resin and it is essential to use ones having a high molecular weight, and that the presence of the monoepoxy compound prevents water dispersibilization, resulting in not obtaining an electrodeposition coating composition having good stability, and further has such drawbacks that the coated film has high gloss and that it is impossible to obtain a film having good mechanical properties. On the other hand, the use of a polyepoxy compound having at least two epoxy groups has such drawbacks that the stabilization of the emulsion is spoiled during heating of the emulsion, resulting in producing coarse particles and agglomerates in the emulsion, and that an electrodeposited film formed by subjecting the resulting emulsion containing the coarse particles and agglomerates to the electrodeposition coating is highly hydrophobic and shows poor suitability for a water-washing treatment to remove an electrodeposition coating composition which has electrodeposited excessively with water, and the coated film shows poor finish appearance.
Japanese Patent Application Laid-Open No. 75575/89 discloses a resin composition for use in the electrodeposition coating, which composition comprises a fluorine-containing polymer having carboxyl group and hydroxyl group, and an organoalkoxysilane compound as the film-forming components. The above resin composition is such a resin composition as to be prepared from a resin composition for use in the electrodeposition coating, which contains a fluorine-containing polymer having carboxyl group and hydroxyl group and an amino resin as the film-forming components, by using the organoalkoxysilane compound in place of the amino resin as the crosslinking agent in order to improve properties such as weather resistance, heat resistance, electrical insulating properties, and the like. However, it is difficult to obtain a matte film from the resin composition disclosed as above.